In traditional Long Term Evolution (LTE) cellular communication, voice, data and other traffic between two UEs are exchanged through evolved NodeBs (eNBs) where they reside, and a core network.
D2D, which is a direct communication technology between UEs, refers to that data are transmitted between the adjacent UEs in a short-distance range over a direct link, without being forwarded by a central node (i.e., a base station).
The LTE D2D technology refers to D2D communication controlled by an LTE network in an LTE licensed frequency band. The LTE D2D technology has been introduced to enable the LTE technology to evolve from the simple radio mobile cellular communication technology toward the universal connectivity technology.
Unlike cellular communication, a node transmitting data to a UE in D2D is another UE, as illustrated in FIG. 1. Data transmitted by a User Equipment A (UE, or referred to a terminal) in FIG. 1 is received by a UE B. In D2D communication, transmit power of the UE as the transmitting end is adjusted similarly to uplink transmit power in LTE cellular communication. The D2D link refers to a link in D2D communication, and an N2D link refers to a link between an eNB and a UE in cellular communication.
However there has been absent so far a particular solution to adjusting transmit power of a UE as the transmitting end in D2D communication, if the transmit power of the UE as the transmitting end is adjusted in the same way as uplink transmit power in LTE cellular communication, then there may be considerable interference upon other UEs in a cellular network (a UE in cellular communication over the cellular network, and a UE in D2D communication over the cellular network).